Diagnosis Method for an Exhaust Gas Post-Treatment System

• US 20080103684A1
• Filed: 01/19/2006
• Published: 05/01/2008
• Est. Priority Date: 02/03/2005
• Status: Active Grant

• Current Assignee: AVL List GmbH (List Privatstiftung)
• Original Assignee: AVL List GmbH (List Privatstiftung)
• Inventors: Huss, Arno, Allmer, Ingo, Huelser, Holger
• Granted Patent: US 8,286,417 B2
• Time in Patent Office: Days
• US Class Current: 701/114
• CPC Class Codes: B01D 53/9431 Processes characterised by a specific device
• CPC Class Codes: B01D 53/9495 Controlling the catalytic process
• CPC Class Codes: F01N 11/00 Monitoring or diagnostic devices for exhaust-gas treatment apparatus , e.g. for catalytic activity safety, indicating or supervising devices for internal combustion engines F02B77/08; testing of machines G01M13/00
• CPC Class Codes: F01N 2260/14 for modifying or adapting flow area or back-pressure
• CPC Class Codes: F01N 2430/06 by varying fuel-air ratio, e.g. by enriching fuel-air mixture
• CPC Class Codes: F01N 2430/08 by modifying ignition or injection timing
• CPC Class Codes: F01N 2550/02 Catalytic activity of catalytic converters
• CPC Class Codes: F01N 2560/026 for measuring or detecting NOx
• CPC Class Codes: F01N 2560/06 the means being a temperature sensor
• CPC Class Codes: F01N 2570/14 Nitrogen oxides
• CPC Class Codes: F01N 2610/02 the substance being ammonia or urea
• CPC Class Codes: F01N 3/023 using means for regenerating the filters, e.g. by burning trapped particles by electrically controlling the supply of combustible mixture or its constituents only F02D41/0235
• CPC Class Codes: F01N 3/0235 using exhaust gas throttling means
• CPC Class Codes: F01N 3/2006 Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating by electrically controlling the supply of combustible mixture or its constituents only F02D41/0235
• CPC Class Codes: F01N 3/206 Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents F01N3/2066 takes precedence
• CPC Class Codes: F01N 9/005 using models instead of sensors to determine operating characteristics of exhaust systems, e.g. calculating catalyst temperature instead of measuring it directly
• CPC Class Codes: F02B 29/0406 Layout of the intake air cooling or coolant circuit
• CPC Class Codes: F02B 37/00 Engines characterised by provision of pumps driven at least for part of the time by exhaust
• CPC Class Codes: F02B 37/22 by varying cross-section of exhaust passages or air passages , e.g. by throttling turbine inlets or outlets or by varying effective number of guide conduits F02B37/24 takes precedence
• CPC Class Codes: F02D 41/0055 Special engine operating conditions, e.g. for regeneration of exhaust gas treatment apparatus
• CPC Class Codes: F02D 41/146 : the characteristics being an NOx content or concentration
• CPC Class Codes: F02D 41/1463 : of the exhaust gases downstream of exhaust gas treatment apparatus
• CPC Class Codes: F02M 26/05 : High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
• CPC Class Codes: F02M 26/23 : Layout, e.g. schematics
• CPC Class Codes: Y02A 50/20 : Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02T 10/12 : Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 : Engine management systems

Abstract

The invention relates to a diagnosis method for an exhaust gas post-treatment system for the reduction of nitric oxides in the exhaust gas train of an internal combustion engine by means of selective catalytic reduction. The following steps are provided for easy recognition of errors: definition of at least one threshold value for the No_x concentration for at least one engine operation point; shifting the operational mode of the internal combustion engine into an operational state of diagnosis, wherein in the operational state of diagnosis substantially more No_x emissions are produced than in the normal operational mode; determining an amount of reducing agents corresponding to the increased amount of No_x emisions in the operational state of diagnosis; controlling a dosing device in order to introduce the amount of reducing agents, corresponding to the increased amount of NO_x emissions during the operational state of diagnosis, into the wase gas; measuring the concentration of NO_x downstream from the post-treatment device; comparing the measured concentration of NO_x to the threshold value; taking a decision as to the erroneous or error-free operation of the waste gas post-treatment system based on comparison of the measured concentration of NO_x to the threshold value; terminating the operational state of diagnosis.

Claims

1-24. -24. (canceled)

25. Method for diagnosing an exhaust gas treatment system for reduction of nitrogen oxides in an exhaust gas train of an internal combustion engine by means of selective catalytic reduction, where a reducing agent is fed into exhaust gas via a metering device, with at least one NO_x-sensitive sensor located downstream of an exhaust gas treatment device, with the following steps:

defining at least one threshold value for NO_x concentration for at least one operating point of the internal combustion engine;

changing an operating state of the internal combustion engine from a usually prevailing normal operating state to a diagnostic operating state, a generated amount of NO_x emissions in a diagnostic operating state being at least twice that of the normal operating state;

determining the amount of reducing agent corresponding to the increased NO_x emissions of the diagnostic operating state;

controlling the metering device in such a way that an amount of reducing agent corresponding to the increased NO_x emissions of the diagnostic operating state is fed into the exhaust gas;

measuring a NO_x concentration downstream of an exhaust gas treatment device;

comparing a measured NO_x concentration to the threshold value;

deciding whether the exhaust gas treatment system is operating properly or malfunctioning, based on a comparison between the measured NO_x concentration and the threshold value; and

terminating the diagnostic operating state, with the internal combustion engine being switched back to the normal operating state or to a sensor diagnostic operating state for checking the proper functioning of the NO_x sensitive sensor.

27. Method according to claim 25 or 26, wherein the generated amount of NO_x emissions in a diagnostic operating state is at least five times that of the normal operating state.

28. Method according to claim 25 or 26 with the following steps:

changing an operation of the internal combustion engine from a usually prevailing normal operating state or the diagnostic operating state to a sensor diagnostic operating state, with a generated amount of NO_x emissions in a sensor diagnostic operating state being greater than that of the normal operating state;

determining the amount of reducing agent corresponding to the increased NO_x emissions of the sensor diagnostic operating state;

controlling the metering device in such a way that an amount of reducing agent is fed into the exhaust gas, which is less by a defined deficiency amount than that required for complete reduction of the NO_x emissions, thus resulting in a NO_x concentration downstream of the exhaust gas treatment device which is higher than the sensitivity threshold of the NO_x sensitive sensor;

determining a residual NO_x concentration based on the defined deficiency amount of reducing agent;

measuring the NO_x concentration downstream of the exhaust gas treatment device by means of the NO_x sensitive sensor;

comparing the measured NO_x concentration with the determined residual NO_x concentration;

deciding whether the NO_x sensitive sensor downstream of the exhaust gas treatment system is functioning properly or malfunctioning; and

terminating the sensor diagnostic operating state, preferentially switching back to the normal operating state.

29. Method according to claim 25 or 26, wherein the internal combustion engine is operated in the diagnostic operating state or in the sensor diagnostic operating state with modified exhaust gas recirculation rate as compared with the normal operating state.

30. Method according to claim 29, wherein the internal combustion engine is operated with reduced exhaust gas recirculation.

31. Method according to claim 25 or 26, wherein the internal combustion engine is operated in the diagnostic operating state or in the sensor diagnostic operating state with modified cooling of the recirculated exhaust gas mass flow, as compared with the normal operating state.

32. Method according to claim 31, wherein the internal combustion engine is operated with reduced cooling of the recirculated exhaust gas mass flow.

33. Method according to claim 25 or 26, wherein the internal combustion engine is operated in the diagnostic operating state or in the sensor diagnostic operating state with modified boost pressure, as compared with the normal operating state.

34. Method according to claim 33, wherein the internal combustion engine is operated with increased boost pressure.

35. Method according to claim 25 or 26, wherein the internal combustion engine is operated in the diagnostic operating state or in the sensor diagnostic operating state with modified fuel injection timing, as compared with the normal operating state.

36. Method according to claim 25 or 26, wherein the internal combustion engine is operated in the diagnostic operating state or in the sensor diagnostic operating state with modified fuel injection pressure, as compared with the normal operating state.

37. Method according to claim 25 or 26, wherein the NO_x concentration is measured upstream of the exhaust gas treatment device at least during the diagnostic operating state or in the sensor diagnostic operating state, and the amount of reducing agent to be fed into the exhaust gas is determined using the measurement of NO_x concentration upstream of the exhaust gas treatment device.

38. Method according to claim 25 or 26, wherein the amount of reducing agent to be fed into the exhaust gas is determined at least during the diagnostic operating state or the sensor diagnostic operating state with a use of a characteristic map or a model for determining the NO_x emissions of the internal combustion engine.

39. Method according to claim 25 or 26, wherein in the diagnostic operating state or the sensor diagnostic operating state a torque of the internal combustion engine is adjusted to equal the torque in the normal operating state by modifying the amount of injected fuel.

40. Method according to claim 39, wherein the torque of the internal combustions engine is adjusted by increasing the amount of injected fuel.

41. Method according to claim 25 or 26, wherein switching to the diagnostic operating state or the sensor diagnostic operating state is performed only if at least one defined initial condition, selected from the group engine speed torque of the internal combustion engine or the temperature of the exhaust gas treatment device, are fulfilled.

26. Method for checking the proper functioning of the NO_x sensitive sensor, with the following steps:

changing an operation of the internal combustion engine from a usually prevailing normal operating state or the diagnostic operating state to a sensor diagnostic operating state, with a generated amount of NO_x emissions in a sensor diagnostic operating state being greater than that of the normal operating state;

determining the amount of reducing agent corresponding to the increased NO_x emissions of the sensor diagnostic operating state;

controlling the metering device in such a way that an amount of reducing agent is fed into the exhaust gas, which is less by a defined deficiency amount than that required for complete reduction of the NO_x emissions, thus resulting in a NO_x concentration downstream of the exhaust gas treatment device which is higher than the sensitivity threshold of the NO_x sensitive sensor;

determining a residual NO_x concentration based on the defined deficiency amount of reducing agent;

measuring the NO_x concentration downstream of the exhaust gas treatment device by means of the NO_x sensitive sensor;

comparing the measured NO_x concentration with the determined residual NO_x concentration;

deciding whether the NO_x sensitive sensor downstream of the exhaust gas treatment system is functioning properly or malfunctioning; and

terminating the sensor diagnostic operating state, switching back to the normal operating state.

42. Device for diagnosing an exhaust gas treatment system for reduction of nitrogen oxides in an exhaust gas train of an internal combustion engine, wherein the internal combustion engine is provided in the exhaust gas train with an exhaust gas treatment device with selective catalytic reduction, and with a metering device for the reducing agent upstream of the exhaust gas treatment device, and with at least one sensor for measuring NO_x concentration downstream of the exhaust gas treatment device.

43. Device according to claim 42, wherein a temperature sensor is located downstream of the exhaust gas treatment device.

44. Device according to claim 42, wherein a sensor for measuring NO_x concentration is located upstream of the exhaust gas treatment device.

45. Device according to claim 42, wherein the metering device is connected to a control unit, which controls the feeding of reducing agent depending on the actual NO_x emissions of the internal combustion engine.

46. Device according to claim 42, wherein the internal combustion engine is provided with at least one actuating means controlled by the control unit for switching the internal combustion engine from a normal operating state to a diagnostic operating state.

47. Internal combustion engine with an exhaust train, in which is located at least one exhaust gas treatment device, configured as a particulate filter, where regeneration of the exhaust gas treatment device can be initiated by temperature increase of the exhaust gas, wherein at least one variable throttling device is positioned in the exhaust train.

48. Internal combustion engine according to claim 47, wherein the variable throttling device is configured as a flap.

49. Internal combustion engine according to claim 47, wherein the variable throttling device is positioned upstream of the exhaust gas treatment device.

50. Internal combustion engine according to claim 47, wherein the variable throttling device is positioned downstream of a turbine of a turbocharger.

51. Internal combustion engine according to claim 47, wherein the variable throttling device is located downstream of a point where an exhaust gas recirculation line branches off the exhaust train.

52. Method for operating an internal combustion engine, wherein an exhaust gas flow is throttled in operating phases when an operating temperature of the internal combustion engine or of at least one exhaust gas treatment device is below a defined operating temperature, or in operating phases when regeneration of an exhaust gas treatment device is performed.

53. Method according to claim 52 for regeneration of a particulate filter located in an exhaust train of an internal combustion engine, where a regeneration phase of the particulate filter is initiated by a temperature increase of the exhaust gas, wherein a throttling device is closed at least partially in order to initiate a temperature increase of the exhaust gas, and wherein the internal combustion engine is controlled in such a way that no power drop occurs during the regeneration phase.

54. Method according to claim 53, wherein the throttling device is positioned upstream of the particulate filter.

55. Method according to claim 53, wherein the amount of injected fuel is increased during the at least partial closing of the throttling device in order to avoid a power drop.